drm/xe/display: Annotate desc of platforms with display

Some platforms don't have the display IP. Currently those are PVC and
ATS-M. For PVC the current initialization order works as the display
initialization can check by platform. However the display side can't
differentiate ATS-M from DG2 to act accordingly.

Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Link: https://lore.kernel.org/r/20230510195424.3045127-3-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>